deletions | additions       diff --git a/At_installation_time_the_beam__.tex b/At_installation_time_the_beam__.tex  index fd8f677..43730fc 100644  --- a/At_installation_time_the_beam__.tex  +++ b/At_installation_time_the_beam__.tex 
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The initial coarse alignment of a beam train (requirement 1) takes place using the BCA primary fiducial as before (there exist additional options to use the UTM light injector in addition to or instead of the primary fiducial for this task, but for brevity discussion of these options will be left to a later date).  The start-of-night alignment (requirement 2) is changed from the original scheme. Instead of using the primary fiducial, the UTM light injector is switched on. The location of the spot seen on the FTT camera is set to be the fiducial point to which the FTT servoes starlight; as a result all subsequent starlight beams will have the same tilt as the injected beam. At the same time the shear of the injected beamin the BCA  is measured using BEASST. The tilts of M4 and M5 are adjusted so that the measured shear coincides with a fiducial point on BEASST and does not change when the DL is moved backwards and forwards: this condition means that the injected beam is aligned with the DL axis. At this point, the primary fiducial can be switched on and aligned with the UTM injected beam, using BEASST to compare the tilt and shear of the two beams. Further alignment of the fringe tracker and piston terms (requirements 4 and 5) can then proceed as in the original system.